Under normal operating conditions, a bearing chamber of a gas turbine engine typically contains a lubricating oil. Pressurised seals are used to prevent oil leakage from the bearing chambers into the rest of the engine. With such a seal, the bearing chamber is held under a negative pressure. To maintain the negative pressure, air is bled out of the bearing chamber. The air bled from the bearing chamber typically contains an amount of oil in the form of droplets or particles. This mixture of air and oil droplets is then passed to an oil/air separator, such as a centrifuge which rotates at high speed. The separated oil is returned to the lubrication system while the air is discharged overboard through a breather outlet.
Although, in general, oil/air separators are unable to remove absolutely all of the oil from the air which is discharged overboard, it is desirable to improve the efficiency of the separator in order to reduce the environmental impact of the engine. However, high efficiency separators effectively eliminate oil consumption, which over time can cause the oil to thermally degrade, becoming acidic and leaving deposits around the oil system. Furthermore, the oil can become less effective at performing its function of heat and debris transference. To overcome this problem, it is necessary to monitor the oil to identify when partial or full oil change is required.
Moreover, the oil/air mixture discharged overboard may have the appearance of smoke, particularly when the aircraft is stationary or moving relatively slowly. This may cause distress to passengers as the smoke may be mistakenly assumed to be a problem with the engine. Furthermore, the oil/air mixture may cause unsightly staining of the engine nacelle as it is discharged overboard and may also stain the runway surface.
U.S. Pat. No. 6,513,332 discloses a breather outlet comprising an electromagnetic wave (e.g. microwave) generator which is used to evaporate at least a portion of the liquid dispersion. However, whilst the breather outlet is able to reduce the appearance of smoke, it does not provide any quantitative information regarding the egress of oil from the engine.
It is therefore desirable to provide a fluid management apparatus and method which is able to analyse the oil flow out of the engine and to prevent smoke from forming.